After waterflooding，a great deal of attic oil and by-pass oil was trapped underground in Tahe fractured-cavity carbonate reservoir. Nitrogen flooding can recover part of the remaining oil for its characteristic of low density，prominent gravitational differentiation and so on. Full understanding of the distribution of remaining oil after nitrogen flooding has the vital referential significance to the design optimization of gas drive scheme. Visible physical models were designed and built for nitrogen flooding simulation experiment. The experiment were conducted to intuitive display the distribution of remaining oil after gas drive in the fractured-cavity reservoir，and then the related influencing factors were discussed. Experimental results show that nitrogen flooding can effective enhance oil recovery of the remaining oil after waterflooding，but some oils were still entrapped including oil，called channel-flow oil in this article，held up in the middle of the cave due to the gas channeling and low energy of bottom water，and oil film and small oil slug entrapped in the fractures because of the low displacement efficiency of nitrogen. In the meanwhile，human factors，such as injection modes，injection well type and injection rate，had influence on the remaining oil after gas drive. This study could provide experimental basis for enhancing oil recovery with gas drive and after gas drive. Unbalanced injection mode such as WAG and nitrogen injecting with moderate rate in complex area could improve the effect of gas drive. The shape of caves，the distribution of fracture-cavity and other objective factors were realized to be the important points of further study.